visual information processing in schizophrenia patients with visual hallucinations

Conditions: Schizophrenia; Visual Hallucination; Auditory Hallucination; False Perception

Summary: occurrence of visual hallucinations (vhs) in schizophrenia depend in part on disorders in the processing of late visual information (top-down). the broader question of how these top-down mechanisms (cognitive and / or emotional mechanisms) are involved in the occurrence of vhs remains to be specified and very few behavioral studies have so far been interested. the investigators propose to study the implication of top-down mechanisms in the visual hallucinatory manifestations, more specifically in the processing of ambiguous stimuli during an emotional priming task. schizophrenia patients with vhs would have more false visual perceptions in the treatment of ambiguous stimuli than schizophrenia patients with auditory hallucinations or no hallucinations (ah/nh) and healthy controls.

in schizophrenia patients with auditory hallucinations, top-down mechanism on perceptual processing could be illustrated by tasks of listening to white noise. these studies show that psychotic subjects detect more words and phrases when exposed to these stimuli. in schizophrenia patients with vhs, to our knowledge no study have explored the mechanism of false perception. thus, we propose to experimentally manipulate the implication of top-down mechanisms on visual perception using an emotional priming task. this paradigm has already been used in this population to explain the mechanisms underlying productive symptoms. for example, in an emotional priming task authors have shown that a negative valence primer contributes to the implementation of an interpretive bias in a confidence judgment task. the aim of the present study is to explore the implication of these top-down mechanisms in hallucinatory manifestations, more specifically on the treatment of ambiguous visual stimuli during an emotional priming task by manipulating the emotional valence of the primer. the goal is to determine how emotional environmental elements contribute to the formation of erroneous perceptions in patients with schizophrenia with vhs.

Eligibility criteria:
all groups: * age between 18 and 55 years * affiliation to or benefiting from a social security * visual acuity normal or corrected to normal * person who received and understood the complete information about the organization of the research and gave written and free informed consent before participating in the study group of patients with schizophrenia with visual hallucination (hv) with or without auditory hallucination (ha) (hv group): * schizophrenia according to the diagnostic and statistical manual of mental disorders iv criteria * presence of a hallucinatory visual symptomatology (hv) in the history of the disease measured by the psychosensory hallucination scale (psas). * the presence of a hallucinatory symptomatology in auditory mode (ha) in addition to the hv is not a criterion of non-inclusion. group of patients with schizophrenia either with auditory hallucination (ha) but without visual hallucination (hv) or no hallucination, auditory or visual (nh) (ha / nh group) * schizophrenia according to the diagnostic and statistical manual of mental disorders iv criteria * presence of a hallucinatory symptomatology in auditory mode (ha) in the history of the disease measured by the psas or absence of any hallucinatory manifestations in the history of the disease * absence of visual hallucinatory symptomatology (hv) in the history of the disease as measured by psas

Keywords: schizophrenia visual hallucination false perception emotional priming